The present invention relates to an implantable device that monitors cardiac electrogram feature information, which information can be used to detect and predict the onset of spontaneous cardiac arrhythmias. The electrogram feature information is detected through subcutaneous electrodes. The device can incorporate a defibrillator or other therapeutic shock treatment apparatus for treating cardiac arrhythmias.
Numerous different cardiac arrhythmias are treated through implantable devices. Arrhythmias that can be treated with such devices include atrial and ventricular fibrillation, as well as less pronounced arrhythmias. Since such devices typically contain their own power supply, it is desireable to accurately predict when a therapeutic electrical pulse should be administered so that unnecessary pulses can be avoided. It is also desireable to be able to predict arrythmias in advance of onset or at an early phase, before the arrythmia progresses to a serious stage such as ventricular fibrillation. Accordingly, almost all implantable arrhythmia treatment devices incorporate sensing electrodes and sensing circuitry.
Current sensing electrodes are positioned on the right side of the heart, at the end of the defibrillation lead. Such sensing electrodes collect little information on electrical activity in the left ventricle. Because most arrhythmias originate in the left ventricle, obtaining left ventricle electrical information is highly desireable to providing an indication of risk of arrhythmia. In addition, spatial distribution of sensing electrodes (i.e., separating the electrodes in different locations) is also important, because spatially separate electrodes gather information from a greater volume of heart tissue. But, it is undesireable to place an electrode in the left ventricle because of the risk of clott formation on the catheter, leading to stroke.
In view of the foregoing, there is a continued need for new sensing electrode configurations and techniques that can be employed in implantable arrhythmia treatment apparatus.
A first aspect of the present invention is an implantable apparatus for the detection and monitoring of spontaneous cardiac electrogram features in a patient. In a preferred embodiment, the apparatus is a defibrillator. The apparatus comprises an implantable cardiac monitoring device and a plurality of subcutaneous cardiac sensing electrodes electrically connected to the monitoring device. The sensing electrodes are configured for sensing cardiac electrogram features when implanted in spatially separate locations in a patient. A storage device contained within the monitoring device is operably associated with the subcutaneous electrodes and stores the cardiac electrogram features. Preferably, the plurality of subcutaneous electrodes are carried by a single elongate lead. A downloading device such as telemetry apparatus or transcutaneous electrical connectors may be provided so that the stored information can be downloaded to a separate apparatus external to the patient.
A second aspect of the present invention is a method for detecting cardiac electrogram features in a patient in need thereof. The method comprises providing a plurality of subcutaneous sensing electrodes implanted in spatially separate locations in the patient, providing an implantable cardiac monitoring device operably associated with the subcutaneous sensing electrodes, detecting cardiac electrogram features through the plurality of sensing electrodes, and then storing the detected cardiac electrogram features in the monitoring device. The detected information can be used to administer an appropriate therapeutic electrical pulse to the patient.
The foregoing and other objects and aspects of the present invention are explained in detail in the drawings herein and the specification set forth below.